[ARDF] Fun and Frustration

[bruce]

On Thu, 8 Oct 2009 12:15 pm, Gerald Boyd wrote:
> Hi Bruce.
>

> --My own feeling, and I'm happy to be contradicted, is that power
> consumption,
> --and to a lesser degree cost, often overlooked till it's too late, is the
> --killer for battery powered s/w defined radio solutions at this stage.

> Actel now has a part that is even lower power then the old cool runner,
> However its speed may be to slow for some applications( 30 mhz top).
> in the SDR transmitter we are shutting down power to the Xilinx FPGA when
> its off cycle to save power.

OK for TX :)
...

> Only requires one low cost chip $ 5 to boot an sram based Spartan. However
> the Actel pro asic 3e devices are flash based and don't require any

The original contention was that a SDR could create a cheaper, less 
complicated solution than the RF-and-microcontroller existing solutions. I 
just can't see it happening, once you add all the little $5 and $10 bits 
together. It's the labour and low-run inventory cost, not the parts cost that 
dominate a sniffer cost. (I know... I've been there.)
More flexible, certainly. Also, using some standard existing UI 
(iTouch/iPhone/PDA) also gives you a nifty UI with nice features 
(compass/accerometer), but certainly not cheaper. I also have severe 
reservations about this sort of thing surviving in real ARDF conditions. 
Certainly wouldn't survive a foxhunt here !!
Nevertheless, this could anyway be used in conjunction with an existing 
solution, just replacing the UI.

> external support chips other then a clock source. The FPGA is doing a
> majorityy of the work including LO generation.
OK. Drop the VCO and PLL, but still keep RF mixer and RF front end and IF amp. 
Counts out the 30Mhz parts though. 
You also said the words "just Mini Circuits" which would have to be the most 
expensive RF parts in the world :)

> It maybe be possible to over come the power issue with some newer devices.
> I see articles in industry hinting that newer FPGA are taking over
> processor based applications.
... articles have been saying that for quite a while now.... :)

> Have been doing some functions in FPGA's that 
> 10 years ago I would have used a processor.
Absolutely.
Even 15 years ago I did an FPGA based doppler system.

> --Perhaps a solution where you sample at audio frequencies, or zero IF
> (with I and Q) could be a useful
> that may be where the new actel low power igloo device can rule?

Yes, but what is it actually saving you ?  A diode detector and an IF ceramic 
filter ? (replaced by DSP IF filter and synchronous IQ detector).  I must be 
missing something here.

> --Dale's idea of a separate RF and CPU board is perhaps the most currently
> helpful idea, but bear in --mind that is exactly what the "Ultra Sniffer"
...
> --You are wecome to the circuit and layouts for the old Ultra sniffer RF
> board if you want.
>
> Yes would be interesting to see how it was done.

Will dig them up. Have to wait till after the World Masters !

> --It could still form the basis for a solid performing ARDF receiver, and
> it can double as a F
> --oxOr transmitter too ! The micro board however, by today's standards, is
> crap.
>
> --Lastly, I'd be very surprised if an iPhone can directly do a SDR without
> an external downconversion.
> --See above comment about needing lots of stuff to do even that.
>
> --That's my 2c. As I said, happy to be contradicted as there could be now
> developments of
> --which I'm unaware, as I don't work directly in RF anymore, but for now, I
> concur with Dale.

-- 
Cheers,
Bruce